Planar flow channels for peristaltic pumps

ABSTRACT

A flow channel plate suitable for use with a peristaltic pump comprises: a planar substrate; a flow channel in the planar substrate and mechanical strain relief means in the planar substrate, allowing lateral expansion of the flow channel during vertical compression of the flow channel. The path of the flow channel in the flow channel plate may be nonlinear. The flow channel may be characterized by a Davis-Butterfield cross sectional shape. A roller pump head comprises: a flow channel plate; a roller cage; tapered rollers held in position by the roller cage; and a drive rotor comprising one of a tapered rotor and a rotor having a radially limited zone of contact on the sloping portions of the tapered roller. Lower surfaces of the tapered rollers apply force to the flow channel plate and upper surfaces of the tapered rollers receive force from the drive rotor.

CROSS REFERENCES TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication Ser. No. 62/505,900, entitled “Improved peristaltic pumptechnologies”, filed on May 13, 2017 which is hereby incorporated byreference as if set forth in full in this application for all purposes.

BACKGROUND

Biological systems including tubes or channels such as the intestines orureters perform a fluid pumping action called peristaltic pumping, inwhich waves of smooth muscle contraction move along the length of thebiological tube. In the remainder of this disclosure,naturally-occurring peristaltic pumps in biological systems are referredto as “biological peristaltic pumps”.

Artificial peristaltic pumps which mimic the action of biologicalperistaltic pumps have been developed since 1855. In the remainder ofthis disclosure, the term “peristaltic pump” without the precedingadjective “biological” should be understood as referring to anartificial peristaltic pump.

A peristaltic pump, often called a roller pump, is a fluid pump in whichan enclosed flow channel is compressed by roller or rollers, or by aseries of compression blocks or fingers, to propel a fluid along thechannel from a channel entrance to a channel exit, in rough analogy withthe peristaltic pumping action of biological peristaltic pumps.Advantageously, the fluid being pumped contacts only the interiorsurfaces of flow channel, and complex components such as valves orpistons, which would be subject to leakage or sliding wear, are avoided.

The first peristaltic pump, patented in the US in 1855, employed anelastic tube. Improvements were made but the peristaltic pump was notwidely used before 1932. Currently, peristaltic pumps are ubiquitous,with uses including hemodialysis, cardiopulmonary bypass, pharmaceuticalmanufacturing, drug infusion, chemical handling, slurry pumping, andgeneral laboratory use. There are hundreds of manufacturers ofperistaltic pumps in the USA.

All early versions of peristaltic pumps used soft, round tubes or hoses,and the use of soft, round tubes or hoses continues to the present.

Flow channels for peristaltic pumps having a non-round cross sectionalshape, which herein will be called the Davis-Butterfield shape, or DBshape, after the inventors, potentially have performance advantages overa round tube or hose, including low spallation, low mechanical stress,long channel life, and high pressure capability. There is, however, apotential drawback of this shape, regarding lateral expansion of theflow channel under vertical compression, which has not previously beenacknowledged or discussed. There is, therefore, a need for designs thatdirectly address this issue, facilitating adoption of such channels inperistaltic pumps.

Most existing peristaltic pumps are roller pumps, and most roller pumpscan be called “circumferential roller pumps” as the peristaltic pumptubing is disposed around a curved path on a rigid backing member and isdriven by rollers which compress the tubing against the circumference ofthe curved path. There are, however, several peristaltic pump designswhich can be called “face roller pumps”. In these, the peristaltic pumptubing is disposed on a planar face of a rigid backing member and iscompressed against that planar face by rollers rolling in a circularpath around an axis perpendicular to the planar face.

Wearable insulin pumps are a growing market, mainly for use by Type Idiabetes patients, also known as juvenile diabetes patients. Whencombined with a blood glucose sensor in an electronic feedback loop, theresult can be called an “artificial pancreas.” A typical wearableinsulin pump comprises a small disposable syringe containing insulin,the syringe being driven by a stepper motor controlled by electronics,the whole package being small enough to wear on a belt clip. A typicalwearable insulin pump is the Medtronic Minimed Model 670G. An insulinpump is one type of infusion pump.

Every three days the patient or caregiver using a wearable insulin pumpmust discard the old syringe to minimize bacterial contamination, andmust refill a new syringe with insulin. Installing a new syringe is athirteen-step process, using four separate disposables. It requires goodtwo-handed manual dexterity, with several chances for septiccontamination. For the many Type I diabetes patients who are children,this process can be a daunting task for them and their parents.

Thus, there exists a need for a compact wearable insulin pump having asimpler insulin refill process with reduced chances for septiccontamination.

SUMMARY

The present invention includes a flow channel plate suitable for usewith a peristaltic pump. The flow channel plate comprises: a planarsubstrate; a flow channel in the planar substrate; and mechanical strainrelief means in the planar substrate, allowing lateral expansion of theflow channel during vertical compression of the flow channel. In oneaspect, the path of the flow channel in the flow channel plate isnonlinear. In another aspect, the flow channel is characterized by aDavis-Butterfield cross sectional shape. In yet another aspect, adisposable kit for an infusion pump comprises the flow channel plate ofclaim 1 and one or more additional elements; wherein the flow channelplate and the one or more additional elements are integrated to form asingle assembly.

The present invention further includes a roller pump head comprising: aflow channel plate; a roller cage; tapered rollers held in position bythe roller cage; and a drive rotor comprising one of a tapered rotor anda rotor having a radially limited zone of contact on the slopingportions of the tapered rollers; wherein lower surfaces of the taperedrollers apply force to the flow channel plate and upper surfaces of thetapered rollers receive force from the drive rotor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 (Prior Art) illustrates the basic principle of acircumferential-roller peristaltic pump.

FIG. 2A (Prior Art) illustrates a cross section of a soft, round tube asused in peristaltic pumps, in a relaxed state.

FIG. 2B (Prior Art) illustrates a cross section of the soft, round tubeof FIG. 2A in a compressed state.

FIG. 3 (Prior Art) shows the Davis-Butterfield cross-sectional flowchannel shape in uncompressed and compressed form.

FIG. 4A (Prior Art) illustrates cross sections of a Davis-Butterfieldflow channel in a relaxed state

FIG. 4B (Prior Art) illustrates a cross section of a Davis-Butterfieldflow channel in a compressed state.

FIG. 5 illustrates a semicircular segment of a peristaltic flow channelaccording to one embodiment of the present invention, following a planarpath.

FIG. 6 illustrates a planar flow channel plate according to oneembodiment of the present invention.

FIG. 7 illustrates a cross section of a face roller pump headincorporating a planar flow channel according to one embodiment of thepresent invention.

FIG. 8 illustrates a three-dimensional exploded view of a face rollerpump head incorporating a planar flow channel according to oneembodiment of the present invention.

FIG. 9 illustrates a cross section of a face roller pump headincorporating a planar flow channel according to another embodiment ofthe present invention.

FIG. 10 illustrates a cross section of a face roller pump headincorporating a planar flow channel according to yet another embodimentof the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments described herein include a peristaltic flow channel andmechanical strain relief features disposed in a planar fashion suitablefor incorporation into a compact face-roller peristaltic pump.Embodiments further include a face-roller peristaltic pump incorporatinga peristaltic flow channel disposed in a planar fashion.

FIG. 1 illustrates the basic principle of a prior-artcircumferential-roller peristaltic pump 10. Flexible tube 1 sittingwithin rigid case member 2 contains the fluid to be pumped, and iscompressed by rollers 3 and 4 on arm 5 at regions 6 and 7. If arm 5rotates clockwise, the rollers 3 and 4 move the compression regions 6and 7 clockwise, causing fluid to be sucked in at 8 and expelled at 9.

In FIGS. 2 through 8 in the present disclosure, the orientation of flowchannels is shown such that a roller or other compression member cancompress the flow channel vertically from above or below, and such thatthe lateral dimensions of the flow channel can increase under verticalcompression while the vertical dimension of the flow channel candecrease.

Descriptive language in this disclosure and in associated claims refersto flow channels in the orientations shown in FIGS. 2 through 8, usingterms such as upper, lower, top, bottom, lateral, vertical, width, andheight, but that language is a convenience for purposes of descriptionand explanation of flow channels in those particular orientations, andis not limiting of the invention, nor is the orientation chosen alimitation of the invention.

FIG. 2A shows a cross section taken through a soft, round tube 20 asused for a traditional peristaltic pump, in its relaxed, uncompressedstate. Lumen 21 in the center of the tube is open or patent.

In FIG. 2B the tube is compressed as it would be under a roller andlumen 21 is almost occluded. The tube is considerably wider in itscompressed state than in its relaxed state, as indicated by the spacingof the dotted lines 22.

The word “round” used herein to describe flow channel shapes connotesflow channels having a lumen which, when viewed from inside the lumen,has a shape which is concave everywhere, such as a circle, oval, orellipse. Flow channel shapes having points, cusps, tips, or regionswhich are convex when seen from within the lumen are non-round.

FIG. 3, reproduced from FIG. 5 of U.S. Pat. No. 9,683,562, illustrates aDavis-Butterfield flow channel non-round cross sectional shape. Suchchannels can be formed by extrusion or by lamination of two sheets.Although the figure does not indicate that any lateral expansion of theflow channel occurs under vertical compression, in reality, lateralexpansion of the Davis-Butterfield channel must occur when it iscompressed vertically. FIGS. 4A and 4B are accurately scaled drawingswhich illustrate cross sections taken through a Davis-Butterfield flowchannel and do take lateral expansion into account. FIG. 4A illustratesthe flow channel in its relaxed, uncompressed state with an open lumen41 between shaped walls 42 and 43, each of uniform thickness, the wallsmeeting at tips 44 and 45 having a small radius of curvature and aninterior angle approaching 180 degrees. FIG. 4B illustrates the samechannel in a compressed state, when the lumen opening 41 is reduced butnot fully occluded. In accurately scaling FIG. 4A and FIG. 4B, thechannel perimeter around the interior walls of lumen 41 in FIG. 4A ismade equal to the channel perimeter around the interior walls of lumen41 in FIG. 4B. Dotted lines 46 indicate that the flow channel undergoeslateral expansion as it moves from its relaxed state to a verticallycompressed state.

Thus, whether the flow channel is a round tube, or has aDavis-Butterfield shape, or has some other shape, the flow channelundergoes lateral expansion when it is vertically compressed.

Prior to the present invention, it has been known that theDavis-Butterfield channel shape may be fabricated by extruding a shapedprofile, or by bonding together two separate sheets such that the edgeof the bonded areas forms the tips of the shaped profile. Thepossibility of bonding together two separate sheets such that the shapedprofile of the channel is set within a larger planar area has notpreviously been disclosed, and nor has the issue of fabricating channelswhich are not straight-line in form but instead follow a curving pathwhich is generally planar. The present invention is inspired in part bya realization that the use of a peristaltic pump flow channel followinga curving path, and situated in planar fashion within a larger planararea, would have utility advantages which are worth pursuing forwearable insulin pumps and other uses. But the lateral expansion of theflow channel under vertical compression is a problem which must beaddressed to use such channels successfully.

FIG. 5 is a perspective view of a flow channel 50 with openings 51 and52 formed by bonding together two separate sheets such that the channelfollows a semicircular path within a plane. The channel shown has aDavis-Butterfield cross sectional shape with channel width 54 andchannel height 55, and the center of the flow path follows a semicirclehaving a radius 53. In one embodiment, radius 53 has a value of 5millimeters; in another, 10 centimeters. The edges of channel 50 wouldbe free to expand within the plane when the channel is compressedvertically if channel 50 were unconstrained in that plane. But ifchannel 50 were set within a larger planar area of bonded sheets, itslateral expansion under vertical compression would be constrained by thepresence of material outside the channel, making its use as aperistaltic pump channel problematic and leading to early failure ofsuch a channel. This problem exists whether the channel has a DB-shapeas shown, or a round channel shape, or some other shape.

That problem of constrained lateral expansion can be addressed byintroducing strain relief means situated outside the edges of thechannel. FIG. 6 illustrates a planar flow channel plate 60 of thepresent invention which can be formed by laminating together twoseparate sheets of material that include stain relief means. Flowchannel plate 60 includes a flow channel 601 shown as having aDavis-Butterfield cross sectional shape, and which has a semicircularportion 68 plus two straight portions 69. The flow channel has openings61 and 62. The dimension 63 is called the pump diameter having a valueof, as one example, 10 millimeters or, as another example, 20centimeters, and extends from the center of the flow path on one side ofthe semicircular path 68 portion of flow channel 601 to the center ofthe flow path on the other side. The flow channel 601 has a channelwidth 64 and a channel height 65. Strain relief means 66 permit portions68 and 69 to expand laterally in the plane of the device when force isapplied from above and/or below the plane of plate 60, for example by aroller, to occlude or partially occlude the flow channel 601 during pumpoperation. Center hole 67 permits a pump drive shaft to pass through theplate 60. The openings 61 and 62 connect to further channel regions, notshown, which may provide a transition from the Davis-Butterfield crosssection (or, in other embodiments, other cross section) shape toconventional round flow channels which can then connect to conventionalround tubing or fittings. Other features, not shown, may be present inflow channel plate 60, for example, through holes or alignment notches,useful for aligning and attaching the flow plate 60 in a peristalticpump head, or laser markings identifying the channel size and shape anddevice serial number.

Strain relief means 66 are shown in FIG. 6 as holes extending throughthe full thickness of flow channel plate 60, but in other embodiments,relief means 66 may comprise recesses extending partly through thethickness of plate 60, or corrugations within plate 60, or thinnedregions within plate 60, or regions prone to bucking under lateralexpansion within plate 60, or inserts of separate material within plate60, or other means of allowing lateral expansion of the flow channel, orcombinations of any of these.

The flow channel plate 60 can be formed by laminating together twoseparate sheets of material or by other means. For example, it can beformed by fine-featured three dimensional printing means known asmicro-stereolithography, using a single printing material or variousmaterials. Other possible means of fabricating flow channel plate 60include, but are not limited to, stereolithography, three-dimensionalprinting, injection molding followed by lamination, vacuum formingfollowed by lamination, lamination around a mandrel, and investmentcasting.

The material comprising flow channel plate 60 may be one or more ofpoly-ether ether ketone (PEEK), polycarbonate, cyclic olefin copolymer(COC), polyvinyl chloride (PVC) with plasticizers, polyvinyl chloridewithout plasticizers, polymethyl methacrylate (PMMA or Plexiglass®),polyethylene, high density polyethylene, ultra high densitypolyethylene, polyethylene terephthalate (PET or PETE), polypropylene,Formlabs printing resin, other printing resin, silicon, glass, siliconerubber, polyimide, stainless steel, brass, and bronze. The use of othermaterials is also possible.

FIG. 7 illustrates a cross sectional view of a face roller pump head 70,according to one embodiment of the current invention, incorporating aflow channel plate and tapered rollers. In the illustrated embodiment,this is flow channel plate 60 having flow channel 601 shown in FIG. 6.Strain relief means 66 are not shown in FIG. 7, for simplicity, butshould be considered to be present within plate 60. Base plate 71 has acentral hole allowing drive shaft 72 to pass through it. Drive shaft 72rotates (as indicated by arrow 79) around a vertical axis (shown asdotted line C. L.) driving tapered drive rotor 73, which frictionallydrives tapered rollers 74, which are held in predetermined relativeangular positions by rotating cage 75. Collar 76 and lip 78 both help tohold the rollers 74 in place radially. Optional shim plate 77 helpsprevent grinding between tapered rollers 74 and flow channel plate 60.

Rollers 74 are tapered to provide non-grinding rotation on shim plate 77over flow channel plate 60, or on flow channel plate 60 if shim plate 77is not present. If cylindrical rollers instead of tapered rollers wereto be used, it is known that a grinding action on the pump componentswould occur. Large cylindrical rollers are sometimes used in grindingmills.

In operation, tapered drive rotor 73 has frictional contact with taperedrollers 74, tapered rotor 73 turning more than twice as fast as cage 75which holds tapered rollers 74. For the approximately 37 degree taperangles of the rollers shown in FIGS. 7 and 8, the drive rotor 73 turnsroughly 2.3 revolutions for every revolution of the cage 75. Therotational speed of the pump head is defined as the rotational speed ofcage 75. A thrust bearing, not shown, attaches to drive shaft 72 beneathbase plate 71 and pulls downward on drive shaft 72 to provide downwardforce on tapered drive rotor 73, which in turn provides downward forceon tapered rollers 74. A spring, not shown, can provide the desireddegree of downward force and may be adjustable. The thrust bearing canbe fixed in position with respect to drive shaft 72, or can beadjustable in position with respect to the drive shaft to provide adesired magnitude of downward force. Other means may be used to providethe desired force on the thrust bearing.

Drive shaft 72 may be driven directly by a drive motor, such as astepper motor or a DC motor, or indirectly, by a gear connected to adrive motor, by a drive belt connected to a drive motor, or by othermeans. Electronics and/or computer controllers may be connected to adrive motor to control the position and rotational speed of drive shaft72. Sensors may be attached to drive shaft 72 and/or to cage 75 tomonitor the angular position of drive shaft 72 and/or rollers 74.Various other electronics, sensor, and computers may be used inconnection with the use of the pump head.

A retention collar, not shown, may be firmly attached to drive shaft 72above base plate 71 and extending loosely beneath cage 75, so that itdoes not contact the cage nor the other pump structures when the pumphead is fully assembled, but when the pump head is disassembled, thecage, rollers, rotor, and drive shaft can be lifted upward as a singleassembly. Further, drive shaft 72 may include (not shown) means, such asa groove or collar, of snapping downward into a rotatable retentionstructure such as a spring-loaded retention structure beneath base plate71 during pump head assembly, and of coming quickly out of the retentionstructure during pump head disassembly, thus enabling different flowchannel plates to be swapped in and out of the pump head quickly andeasily. A thrust bearing, not shown, may be connected to the retentionstructure.

The cross section view in FIG. 7 shows two tapered rollers 74 directlyopposed to each other for illustration purposes, but this is nottypical. Typically there are three tapered rollers 74 in the pump head70 design spaced 120 angular degrees apart from each other, and whenthree rollers are used no cross section can be taken as in FIG. 7 whichwould show two rollers directly opposed.

FIG. 8 is a three-dimensional rendering, slightly exploded, of pump head70. Three tapered rollers 74 can be seen sitting 120 angular degreesapart from one another in cage 75. The tapered rollers 74 are held inplace in cage 75 by axle pins, not shown, comprising part of cage 75,the axle pins engaging recesses, not shown, in the ends of the rollers74. Alternatively, full axles, not shown, extending through each rollerand attached to cage 75, may be used. The contact between axle pins androller recesses may be optimized for low friction, for example by usingjeweled bearings as in watchmaking, by using coatings of diamond-likecarbon on one or both of pins and recesses, or by using ceramic rollersor ceramic pins. Because the fluid flow path of the peristaltic pump isseparated from the pump head mechanism by the walls of the peristalticflow channel, it is also possible to use lubricants such as oil orgrease in the pump head for low friction operation.

Cage 75 may be a unitary body into which the rollers can be snapped intoplace, or may be an assembly which can be assembled around the rotors.

An advantage of the pump head 70 design, as opposed to previousface-roller pump designs in the prior art, is that little or no force isexerted on the axle pins or axles by the tapered rollers. Instead, allof the vertical bearing force coming from drive shaft 72 is exerted bythe tapered rotor 73 on the rollers 74, and by the rollers 74 on theunderlying structures 77, 60, and 71. Thus, a much greater force can besafely applied by a thrust bearing to the drive shaft, enabling muchbetter high pressure operation than was possible with prior art designs,where the allowable force magnitude on roller axles limits high pressureperformance. Collar 76 and rotor lip 78 act to contain the tendency ofthe rollers to slide radially outward during pump operation.

In pump head 70, fluid flow in straight sections 69 of the peristalticflow channel 601 passes between base plate 71 and collar 76.Advantageously, one or both of base plate 71 and collar 76 can featureshallow recessed areas such as shallow recessed areas 79 to avoidvertical pinching of the fluid flow channel in straight sections 69between the base plate 71 and the collar 76. In FIG. 8, shallow recessedareas 79 are present in base plate 71 to serve this purpose. Rollers 74pass over recessed areas 79 during pump head operation, and recessedareas 79 can be designed laterally in a manner, not shown, so thatroughly half of the roller bearing area on flow channel plate 60 remainssupported by underlying base plate 71 as the rollers 74 roll overrecessed areas 79.

The pump head 70 is shown in FIG. 8 as having three tapered rollers 74,but in other embodiments more or less than three rollers may be used, inrough analogy with the design of thrust bearings which may havedifferent numbers of tapered rollers.

An advantage of using more than three rollers is that the volume offluid trapped in the flow channel between adjacent rollers is reduced.When three rollers spaced 120 angular degrees apart are used, theminimum fluid aliquot which can be expelled from the pump is the volumetrapped in a 120-degree segment of the flow channel flow channel. Whenfive rollers are used, a 72-degree segment of the flow channel volumecomprises the minimum aliquot. Thus using a flow channel with a smallcross sectional area, and using as many rollers as feasible, enables thepump head 70 to more easily compete with the minimum aliquot availablefrom syringe pumps presently used in wearable insulin pumps.

The pump head embodiments shown in FIGS. 7 and 8 have drive shaft 72pulling on tapered drive rotor 73 from beneath. In other embodiments,the drive shaft can push on the tapered drive rotor from above.

The pump head embodiments shown in FIGS. 7 and 8 use a tapered driverotor having contact areas between the rotor 73 and the tapered rollers74. The rotor 73 as shown in FIG. 7 has a radially large contact zonewith rollers 74, the zone extending over the length of the sloping wallsof rollers 74 and making contact with each roller at a broad contactpatch.

In other embodiments, a different rotor may have contact with rollers 74along a radially limited zone of contact instead of the radially largerzone of contact present if a tapered drive rotor is used.

FIG. 9 illustrates one such embodiment of the invention, as pump head90, much like pump head 70 in FIG. 7, except that tapered rotor 73 isreplaced with a stepped rotor 93. Drive shaft 92 extends upward to firstsurface 901, and surface 901 extends radially outward to O-ring gland905 which holds O-ring 904. Rotor 93 then steps upward to surface 903which extends radially outward to roller retention lip 98. For purposesof discussion and in the claims below, the rotor 93 is considered toinclude O-ring 904.

In operation of pump head 90, tension force on drive shaft 92 istransferred to rotor 93, and thence to O-ring 904, which bearsvertically downward on the tapered rollers 74 along a radially-limitedzone of contact 906. The zone of contact intersects each roller at asmall contact patch, not shown, similar to the contact patch of arolling automobile tire on pavement. As is the case with pump head 70,the rotor 93 turns roughly 2.3 revolutions for every revolution of thecage 75 for the value of angular taper shown.

FIG. 10 illustrates another embodiment of the invention, as pump head100, much like pump head 70 in FIG. 7, except that tapered rotor 73 isreplaced with a rotor 103 which has no roller retention lip similar tolip 98 or lip 78. Drive shaft 103 extends upward to first surface 1001,and surface 1001 extends radially outward to O-ring gland 1005 whichholds O-ring 1004. Rotor 93 then terminates its outward radialextension. For purposes of discussion and in the claims below, the rotor103 is considered to include O-ring 1004.

In operation of pump head 100, tension force on drive shaft 102 istransferred to rotor 103, and thence to O-ring 1004, which bearsvertically downward on the tapered rollers 74 along a radially-limitedzone of contact 1006. As is the case with pump head 70, the rotor 103turns roughly 2.3 revolutions for every revolution of the cage 75 forthe value of angular taper shown.

In other embodiments, not shown, with non-tapered rotors, theradially-limited zone of contact can be broadened, relative to zones 906or 1006, by using an elastomeric band encircling the rotor, the bandsurface being angled to follow the tapered surfaces of the rollers 74and providing a flat contact area to rotors 74. For purposes ofdiscussion and in the claims below, a rotor having an elastomeric bandencircling the rotor is considered to include the elastomeric band.

For good pump performance it is important to have a non-skid interfacebetween rotor 73 and rollers 74, or between O-ring 904, 1004 and rollers74, or between an elastomeric band, not shown, and rollers 74. Anon-skid interface between rollers 74 and plate 60, or between rollers74 and shim plate 77, is desirable but less important, especially forthree-day disposable applications. Non-skid interfaces may be achievedby various means which will occur to those skilled in pump design.

The rotor 93, 103 may comprise a stiff material having a high elasticmodulus in order provide adequate downward force on the rollers 74through O-ring 904, 1004. O-ring 904, 1004 may be made of a softelastomer for low pressure applications. For high pressure applications,O-ring 904, 1004 may comprise a hard, stiff material with a toughnonskid outer coating. For example, the O-ring may comprise a corehaving the form of a stainless steel coil spring and a coating layer ofpolyimide.

Tapered rotor 73 shown in FIG. 7 has an advantageous characteristic ofbeing self-centering with respect to tapered rollers 74 in cage 75, dueto one of gravitational force in the orientation shown and tensionapplied by other means on the drive shaft 72, because the taperedsurface of rotor 73 bears on the sloping surfaces of tapered bearings74. Tapered rotor 73 also has the advantageous characteristic of beingself-leveling with respect to the tapered rollers 74 in cage 75, due toone of gravitational force in the orientation shown and tension appliedby other means on the drive shaft 72. The self-centering andself-leveling effects are much like those which would be expected if asmall funnel were dropped into a larger funnel, both funnels having thesame taper angle.

The rotor 93 as shown in FIG. 9 has an advantageous characteristic ofbeing self-centering with respect to the tapered rollers 74 in cage 75,due to one of gravitational force in the orientation shown and tensionapplied by other means on the drive shaft 92, because the radiallylimited contact area of rotor 93 though O-ring 95 falls on the slopingportions of the tapered rollers. Rotor 93 also has the advantageouscharacteristic of being self-leveling with respect to the taperedrollers 74 in cage 75, due to one of gravitational force in theorientation shown and tension applied by other means on the drive shaft72. The self-centering and self-leveling effects are much like thosewhich would be expected if a small wheel on an axle were droppedaxle-first into a funnel.

The rotor 103 as shown inf FIG. 10 has an advantageous characteristic ofbeing self-centering with respect to the tapered rollers 74 in cage 75,due to one of gravitational force in the orientation shown and tensionapplied by other means on the drive shaft 102, because the radiallylimited contact area of rotor 103 through O-ring 105 falls on thesloping portions of the tapered rollers. Rotor 103 also has theadvantageous characteristic of being self-leveling with respect to thetapered rollers 74 in cage 75, due to one of gravitational force in theorientation shown and tension applied by other means on the drive shaft72.

For good performance, force exerted on tapered rollers 74 by a rotorsuch as rotor 93 or 103, the rotor having a radially limited contactarea on the sloping portions of tapered rollers 74 through O-ring 904 or1004, should transmit force though the rollers to bear near the radialcenter of flow of the flow channel 601 in flow channel plate 60, toavoid having too little compression force at the radially inward edge ofthe flow channel 601 or too little compression force near the radiallyoutward edge of the flow channel.

The rotors 73, 93, and 103 have performance advantages over prior-artrotor structures using flat disks or soft washers used to drive rollingelements in peristaltic pump heads.

A rotor comprising a flat disk is unsuitable for use with taperedrollers because a flat disk would have bearing force only at smallregions on the radially outward top surfaces of the rollers, and not onthe sloping portions of the rollers, thereby providing too littlecompressive force on the radially inward extents of the tapered rollerwalls. In addition, a flat disk bearing on the top outward surfaces oftapered rollers, rather than on the sloping portions of the taperedrollers, has no self-centering action.

Prior art has discussed the idea of using a soft washer to drive taperedrollers but has not described an embodiment which does so. A rotorcomprising a soft washer is unsuitable for use with tapered rollers inembodiments like those of the present invention because a soft washercan't provide enough downward bearing force for high-pressure operationof peristaltic pumps, and because the radial position of bearing forceprovided by a soft washer, onto tapered rollers and thence onto a flowchannel such as flow channel 601, is difficult to predict or control. Ifa flat, soft washer were larger in radial extent than the radial extentof tapered rollers 74 it would not provide a self-centering action.

In one embodiment of the present invention, a disposable flow channelplate, such as plate 60, can be combined with other components, such asa septum-puncturing receiver for an insulin cartridge and a flexibletube connected to a hypodermic needle, and integrated to form a kitcomprising a single assembly. Using such a kit could reduce a patient'sinsulin filling process from the thirteen steps typically required for asyringe pump to four steps, would use only one disposable instead offour disposables, and require less dexterity, with less chance of septiccontamination. The four steps required when using a kit of the presentinvention comprise inserting the kit into place in an opened pump head,closing the pump head by snapping an assembly of rotor, roller, cage,and axle into place in an underlying retention structure, attaching aninsulin vial, and running the pump until all air bubbles exit theattached tubing of the kit.

A planar flow channel plate such as flow channel plate 60 can becombined in a manifold with other fluidic elements such as flow channelsand valves.

Multiple parallel flow paths driven by one pump head may be included ina planar flow channel plate similar to plate 60.

Multiple planar peristaltic flow channels driven by multiple pump headscan be formed in a single planar manifold which may incorporate otherfluid elements. Additional fluidic, electronic, or optical elements maybe incorporated in such a planar manifold and may extend outward aboveor below the plane of the manifold.

A flow channel plate such as flow channel plate 60 of the presetinvention need not be made from a single material. Composite orlaminated combinations of more than one material may be used to form theflow channel plate without departing from the scope and spirit of theinvention. As one example, the interior walls of a flow channel in plate60 may comprise hard material while the exterior walls of the flowchannel may comprise softer material, providing the advantage of lowspalling of interior walls while providing the advantage of low closingforce for the channel in low pressure applications. As another example,the strain relief means 66 may comprise soft elastomeric regions whilethe remainder of plate 60 may comprise a harder material.

The use of the Davis-Butterfield cross sectional channel shape isadvantageous in the present invention, but is not a necessity of theinvention. A channel having a round cross sectional shape or other crosssectional shape may be used, with the consequence that the stain reliefmeans 66 must possibly accommodate a larger lateral expansion of theflow channel.

Embodiments described herein provide various benefits. In particular,embodiments provide for planar flow channel plate designs that includestrain relief features that accommodate lateral expansion of the flowchannel during vertical compression of the flow channel during operationwith peristaltic pumps. This benefit is likely to be of great value whenchannels of the DB shape, providing advantages of low spallation, longservice life, and high pressure pumping capability, are involved, butwill be useful for other channel shapes too.

The formation of the flow channel plate in a generally planar shape canallow inexpensive manufacturing for use in medical disposable devices.

A planar flow channel plate can also be advantageous in allowing forrapid interchange of flow channels in a pump head for uses such asmedical disposable use.

A three-roller pump head with tapered rollers has been designed to usethe planar flow channels in a manner that provides low stress on theroller axle pins or axles for long service life of the pump head, eitherwhen used with disposable channels or when used with long-service-lifeflow channels. The load on the pump rollers can be adjusted using aspring-loaded thrust bearing attached to the pump's drive shaft toprovide partial or full flow channel occlusion during use and to adjustthe overpressure value at which desired leakage through the flow channelcan occur.

The benefits discussed are likely to be of great value in medicalapplications, such as insulin pumps, and also in many other applicationsin manufacturing and in laboratories in general.

Although the description has been described with respect to particularembodiments thereof, these particular embodiments are merelyillustrative, and not restrictive.

It will also be appreciated that one or more of the elements depicted inthe drawings/figures can also be implemented in a more separated orintegrated manner, or even removed or rendered as inoperable in certaincases, as is useful in accordance with a particular application.

Thus, while particular embodiments have been described herein, latitudesof modification, various changes, and substitutions are intended in theforegoing disclosures, and it will be appreciated that in some instancessome features of particular embodiments will be employed without acorresponding use of other features without departing from the scope andspirit as set forth. Therefore, many modifications may be made to adapta particular situation or material to the essential scope and spirit.

I claim:
 1. A flow channel plate suitable for use with a peristalticpump, the flow channel plate comprising: a planar substrate; a flowchannel in the planar substrate; and mechanical strain relief means inthe planar substrate, allowing lateral expansion of the flow channelduring vertical compression of the flow channel.
 2. The flow channelplate of claim 1, wherein the path of the flow channel in the flowchannel plate is nonlinear.
 3. The flow channel plate of claim 1 whereinthe flow channel is characterized by a Davis-Butterfield cross sectionalshape.
 4. The flow channel plate of claim 1, wherein the planarsubstrate has a full thickness; and wherein the mechanical strain reliefmeans comprises holes extending through the full thickness.
 5. The flowchannel plate of claim 1, wherein the planar substrate has a fullthickness; and wherein the mechanical strain relief means comprisesrecesses extending only partway through the full thickness.
 6. The flowchannel plate of claim 1 wherein the mechanical strain relief meanscomprises a region of elastomeric material.
 7. The flow channel plate ofclaim 1 wherein the mechanical strain relief means comprises one or morecorrugations.
 8. The flow channel plate of claim 1 wherein themechanical strain relief means comprises a region prone to bucklingunder lateral expansion.
 9. A disposable kit for an infusion pump, thekit comprising: the flow channel plate of claim 1; and one or moreadditional elements; wherein the flow channel plate and the one or moreadditional elements are integrated to form a single assembly.
 10. A flowsystem comprising: the flow channel plate of claim 1; and one or moreadditional elements; wherein the flow channel plate and the one or moreadditional elements are connected to form a manifold.
 11. The flowchannel plate of claim 1, wherein the plate material comprises one ofpoly-ether ether ketone, polycarbonate, cyclic olefin copolymer,polyvinyl chloride with plasticizers, polyvinyl chloride withoutplasticizers, polymethyl methacrylate, polyethylene, high densitypolyethylene, ultra high density polyethylene, polyethyleneterephthalate, polypropylene, Formlabs printing resin, other printingresin, silicon, glass, silicone rubber, polyimide, stainless steel,brass, and bronze.
 12. A method of making the flow channel plate ofclaim 1, the method comprising at least one of microstereolithography,stereolithography, three-dimensional printing, lamination, injectionmolding followed by lamination, vacuum forming followed by lamination,lamination around a mandrel, and investment casting.
 13. A roller pumphead comprising: a flow channel plate; a roller cage; tapered rollersheld in position by the roller cage; and a drive rotor comprising one ofa tapered rotor and a rotor having a radially limited zone of contact onthe sloping portions of the tapered rollers; wherein lower surfaces ofthe tapered rollers apply force to the flow channel plate and uppersurfaces of the tapered rollers receive force from the drive rotor. 14.The roller pump head of claim 13, further including one of a collararound the path of the tapered rollers to aid in roller retention, and alip on the drive rotor to aid in roller retention.
 15. The roller pumphead of claim 13, further including a drive shaft connected to the driverotor.
 16. The roller pump head of claim 15, further including a thrustbearing connected to the drive shaft.
 17. The roller pump head of claim16, further including a spring exerting force on the thrust bearing. 18.The roller pump head of claim 16, further including an adjustable springexerting force on the thrust bearing.
 19. The roller pump head of claim13 wherein the drive rotor is tapered.
 20. The roller pump head of claim13 wherein the drive rotor has a radially limited zone of contact on thesloping portions of the tapered rollers.